Assessment of Fire Damage to a Reinforced Concrete Structure during Construction

Abstract

This article summarizes an engineering evaluation of the extent of fire damage to a concrete structure under construction. The fire occurred in a portion of the reinforced concrete structure and visibly damaged a load bearing exterior foundation wall. The purpose of the assessment was to promptly evaluate the in situ condition of the wall and recommend necessary repair or replacement options prior to commencement of backfilling and the concrete construction to be supported by the subject wall. The engineering assessment of the damaged wall included a nondestructive evaluation phase consisting of ultrasonic pulse velocity testing and a laboratory testing phase on the concrete cores removed from the damaged wall. Dynamic Young’s modulus of elasticity and an air permeability index of 25mm(1in.) thick disks sawed from the cores were determined. Analysis of properties of 25mm(1in.) concrete specimens permitted assessment of the presence and degree of any damage in smaller depth increments compared to the size of a compressive strength core. Significant differences were not indicated by compressive strength of cores, however, the in situ nondestructive testing and laboratory testing of the disks were effective in determining the depth of damage, as a result of the fire. The results of the nondestructive and laboratory evaluation indicated that the distressed zone of the concrete was limited to a near-surface layer. Repair recommendations were based on removal and replacement of the affected concrete sections identified by the testing program.